This project is investigating factors, both biological and mechanical, which promote the pathologic deposition of calcium on polyurethane bladders in left ventricular cardiac assist devices fabricated from polyurethane polymers. The pumps, designed by Thermo Electron, are being implanted in calves for periods ranging from 1 to 6 months and the polyurethane bladders studied by morphologic and biochemical analysis for protein, calcium binding properties and lipid content to document changes in the bladder, the pseudointimal (PNI) lining and blood contacting surface. Morphologic methods of analysis (light microscopy and transmission and scanning electron microscopy) coupled with direct enzyme analysis (for acid and alkaline phosphatase) are allowing us to determine if calcification is a dystrophic process associated with cell death or whether osteogenic-like cells are present creating a local environment for mineralization. The proposed studies also focus on the identification of known calcium binding proteins accumulated in the PNI from either circulating serum or by de novo synthesis by cells in the PNI. Two calcium binding amino acids, phosphoserine and gamma-carboxyglutamic acid (G1a) have been identified in the calcium deposits. Further, the vitamin K dependent synthesis of Gla was detected in cultured explants of the formed PNI on the bladder surface. Immunologic techniques will now be utilized to determine the origin of the calcium binding proein as to whether they are similar to blood or bone proteins. Inhibitors of calcification and the effect of warfarin anticoagulation on calcification are being examined in vivo and by modification of the polyurethane polymer.